This invention relates to a communications system using an electromagnetic energy reflector or mirror kept in outer space by electromagnetic radiation pressure.
Good non-cable television reception generally requires line-of-sight transmission. To increase line-of-sight range, a television broadcasting station can increase the height of its transmission antenna. However, due to construction costs, weight, wind, and other factors, the height of a television antenna is limited. One method to increase the line-of-sight range of television reception is to locate relay stations to receive television signals by a long cable or line-of-sight transmission from a television broadcasting station and then to rebroadcast the signals to television sets in the vicinity of the relay station.
To extend the range of television reception the reflector mirror could be attached to an earth satellite. However, an earth satellite would, in general, move with respect to the surface of the earth and stay above the horizon only for a few minutes at a time (approximately less than 10 minutes when the height is approximately less than 600 kilometers). That, together with the expensive cost of satellite launching, makes this an unattractive possibility. Earth satellites, whether stationary or not, do not require energy transmitted from the earth to stay in orbit.
A stationary earth satellite equipped with a large reflector communications mirror would serve the desired purpose. Given sufficient power, it could beam programs to viewers located almost anywhere on about one-half of the earth's total surface. For such a satellite, the height is necessarily about 36,000 kilometers. If the wavelength equals 2 meters and the antenna's radius equals 1.2 kilometers, then the radius of the reflector communications mirror must be greater than approximately 36 kilometers. A mirror of this size would have to be assembled in orbit.
Expensive and sophisticated equipment is required to receive signals from existing communication satellites. Presently these reflected or retransmitted signals are eventually received by TV relay stations to be rebroadcast along line-of-sight to TV sets in the vicinity. Such satellites operate above the earth's ionosphere where ionospheric interference with signal transmission from and to the earth is found. Such satellites operate with decreased transmission efficiency because of the great distances involved. Thus even with satellites, most television viewers today are able to receive only programs beamed to them from a relay station located nearby. In those areas where there are no relay stations, or where existing stations do not transmit programs which some viewers wish to receive, good reception of desired programs is usually impossible. These difficulties could be avoided only if the need for local relay stations could be eliminated. There is also presently lacking an effective means for over-the-horizon radar and a means to impart a high electromagnetic radiation intensity to a wide area on the ground.